Engineering Commons^™

Photochemical Etching Of Nitrided Stainless Steel Piston Rings, Steven Sonntag

Mechanical Engineering Undergraduate Honors Theses

Piston rings are designed to provide a seal between the piston and the cylinder wall of internal combustion engines, keeping oil from the crankcase from getting into the combustion chamber. This means piston rings are the main point of contact between the piston and the cylinder wall, which causes the piston to experience high amounts of friction and wear. By texturing the surfaces of the cylinder wall and/or the piston ring, the amount of contact area can be reduced, allowing for less friction, slower wear, and better gas mileage. In this thesis experiments, photochemical etching processes were developed to etch …

Incorporation Of Silica Nanoparticles Into The Underlayer Of Pda/Ptfe Thin Coatings, Adedoyin Abe

Mechanical Engineering Undergraduate Honors Theses

Polytetrafluoroethylene (PTFE) is one of the most low friction and corrosion resistant solid lubricants. Prior studies have shown that a polydopamine (PDA) underlayer enhances the durability of PTFE thin coating. In this study, 100, 200, and 300 µL of aqueous silica nanoparticle (NP) solutions were added to the PDA deposition solution. The durability and coefficient of friction of PDA/PTFE thin coatings on stainless steel substrates are investigated with and without incorporating the silica NPs. The coatings were tested in dry contact conditions using a Universal Mechanical Tester (UMT) with a ball-on-flat configuration in a reciprocating motion. It was found that …

A Nanoindentation Study Of The Fatigue Properties Of Al/A-Si Core-Shell Nanostructures, Jason Steck

Mechanical Engineering Undergraduate Honors Theses

Nanostructure-textured surfaces can reduce friction and increase the reliability of micro- and nanoelectromechanical systems (NEMS/MEMS). For MEMS incorporating moving parts, the fatigue properties of nanostructures pose a challenge to their reliability in long-term applications. In this study, the fatigue behavior of hemispherical Al/a-Si core-shell nanostructures (CSNs), bare hemispherical Al nanodots, and a flat Al/a-Si layered thin film have been studied using nanoindentation and nano-scale dynamic mechanical analysis (nano-DMA) techniques. Fatigue testing with nano-DMA shows that the deformation resistance of CSNs persists through 5.0 × 10⁴ loading cycles at estimated contact pressures greater than 15 GPa. When the a-Si shell …

Understanding The Evolution Of Surface Texture Under Boundary Lubrication, Salil T. Bapat

Graduate Theses and Dissertations

The objective of this research was to understand the evolution of surface texture under boundary/mixed lubrication (BL). Significant material/energy losses occur during BL because of direct contact between the two surfaces. Traditionally, tribofilms have been studied extensively for BL while textures have been used as a static engineering design parameter to enhance lubricant film properties. However, texture is dynamic at the tribological mating interface, where both physical and chemical interactions are continuously modulated. The evolution and the interplay between the tribofilm and texture is least studied in the literature, which is the focus of this research.

MoS2-based lubricants, known for …

Modeling Residual Stress Development In Hybrid Processing By Additive Manufacturing And Laser Shock Peening, Guru Charan Reddy Madireddy

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

The term “hybrid” has been widely applied to many areas of manufacturing. Naturally, that term has found a home in additive manufacturing as well. Hybrid additive manufacturing or hybrid-AM has been used to describe multi-material printing, combined machines (e.g., deposition printing and milling machine center), and combined processes (e.g., printing and interlayer laser re-melting). The capabilities afforded by hybrid-AM are rewriting the design rules for materials and adding a new dimension in the design for additive manufacturing paradigm. This work focuses on hybrid-AM processes, which are defined as the use of additive manufacturing (AM) with one …

Evaluation Of High Velocity Wear, Armando Deleon

Theses and Dissertations

The HHSTT located at Holloman Air Force Base conducts hypersonic testing in a unique way. Rather than perform cost prohibitive flight testing or hypersonic wind tunnel testing, a rocket-powered sled propels test articles down a track. This test setup has been used to test at speeds up to 2885 m/s (~Mach 8.6). The sled is kept on the rails by utilizing slippers, fabricated to wrap around the rail [1]. This slipper design keeps the sled from separating from the rail during a test due to the airflow producing lift, in a designed effort to minimize the wear that occurs during …

Powder Bed Surface Quality And Particle Size Distribution For Metal Additive Manufacturing And Comparison With Discrete Element Model, Irene Yee

Master's Theses

Metal additive manufacturing (AM) can produce complex parts that were once considered impossible or too costly to fabricate using conventional machining techniques, making AM machines an exceptional tool for rapid prototyping, one-off parts, and labor-intensive geometries. Due to the growing popularity of this technology, especially in the defense and medical industries, more researchers are looking into the physics and mechanics behind the AM process. Many factors and parameters contribute to the overall quality of a part, one of them being the powder bed itself. So far, little investigation has been dedicated to the behavior of the powder in the powder …

Mechanical Wear Debris Feature, Detection, And Diagnosis: A Review, Wei Hong, Wenjian Cai, Shaoping Wang, Mileta M. Tomovic

Engineering Technology Faculty Publications

Mechanical debris is an important product of friction wear, which is also a crucial approach to know the running status of a machine. Many studies have been conducted on mechanical debris in related fields such as tribology, instrument, and diagnosis. This paper presents a comprehensive review of these studies, which summarizes wear mechanisms (e.g., abrasive wear, fatigue wear, and adhesive wear) and debris features (e.g., concentration (number), size, morphology, and composition), analyzes detection methods principles (e.g., offline: spectrograph and ferrograph, and online: optical method, inductive method, resistive-capacitive method, and acoustic method), reviews developments of online inductive methods, and investigates the …

Erosion Degradation Characteristics Of A Linear Electro-Hydrostatic Actuator Under A High-Frequency Turbulent Flow Field, Yuan Li, Shaoping Wang, Mileta M. Tomovic, Chao Zhang

Engineering Technology Faculty Publications

The paper proposes a performance degradation analysis model based on dynamic erosion wear for a novel Linear Electro-Hydrostatic Actuator (LEHA). Rather than the traditional statistical methods based on degradation data, the method proposed in this paper firstly analyzes the dominant progressive failure mode of the LEHA based on the working principle and working conditions of the LEHA. The Computational Fluid Dynamics (CFD) method, combining the turbulent theory and the micro erosion principle, is used to establish an erosion model of the rectification mechanism. The erosion rates for different port openings, under a time-varying flow field, are obtained. The piecewise linearization …